Keep the coffee, water and recipe the same, then change only the burr: the cup can move from dense and integrated to lighter and more separated.

That is why the GU64 burr decision matters. The MP burr and F burr overlap across part of the dial, but they do not use that range in the same way. Which one gives you more room for espresso? Which one gets to a V60 starting point sooner? Can either burr cover both styles without giving up the cup character you enjoy?

This guide turns the measured particle-size differences into three practical answers: which burr to choose, where to start on the dial, and what cup direction to look for while dialing in.

Direct answer

The short version: burr choice and starting settings

Choose the MP burr for an espresso-first setup. Choose the F burr for a pour-over-first setup. The settings below are data-based starting points; adjust in small steps for your coffee and recipe.

Cup directions are sensory hypotheses to test, not results from a controlled cupping. If the brew runs too slowly or tastes dry and bitter, move coarser. If it runs too quickly or tastes thin and sharp, move finer. Espresso may require a finer setting than 25–30 depending on calibration, coffee, basket and dose.

How to read the particle-size data

To compare the two burrs across the dial, we use laboratory particle-size measurements taken at multiple settings between 0 and 80. This shows how the center and width of the grind distribution change as the dial moves coarser.

These measurements are most useful as a relative map: they show how MP and F differ under the same test method. They are not a fixed recipe because coffee, roast, dose, RPM, grinder calibration and brewing equipment can move the setting that works in your kitchen.

Full-range MP vs F results

The tables show four useful views of each sample: D50 for the median particle diameter, D[4,3] for the volume-weighted mean, D90 for the coarse end of the distribution and Span for its relative width.

At matched settings, the F burr generally produces a larger D50 than the MP burr. The difference is largest toward the fine end and narrows toward setting 80. Span also declines as both burrs move coarser, but that alone is not evidence that one burr will always taste cleaner.

MP burr

F burr

Laboratory particle-size measurements under a consistent test method. Use the values to compare the burrs and identify a starting region, then dial in by flow and taste.

D50, Span and surface-area trends

These three trends explain the practical difference between the burrs: how quickly the median moves coarser, how the distribution width changes and how much measured surface area remains at each setting.

D50 trend: where the two burrs overlap

• MP0 is the finest measured sample, at 68.39 μm D50. MP5 measures 85.95 μm.
• At every matched setting from 0 through 70, the F sample has a larger D50 than the MP sample. At setting 80, the values nearly converge: MP80 is 621.9 μm and F80 is 617.7 μm.
• At setting 40, MP measures 448.4 μm and F measures 495.0 μm. The 46.6 μm difference is meaningful, but both medians sit near the medium-fine region of the brew-size reference.
• The F curve begins to flatten at the coarse end: D50 rises by only 10.7 μm between F70 and F80. That means the tested dial number does not translate into a constant particle-size increment.

Span trend: narrower is descriptive, not automatically better

Across the tested positions, the F set has a lower average Span (1.491) than the MP set (1.663). F80 is the lowest reported value at 1.236, while MP5 is the highest at 2.344. That supports a limited statement: the tested F samples generally show a narrower percentile spread relative to their medians.

A lower Span means a narrower relative distribution in this test, but it is not a universal quality score. Puck permeability, fines, alignment, burr geometry, coffee and preparation interact in ways that a single number cannot capture.

Specific surface area: a useful extraction-rate clue

• MP0 reports the highest specific surface area at 44.43 m²/kg; MP5 follows at 40.78 m²/kg.
• F0 reports 27.19 m²/kg, about two-thirds of MP0's value and higher than MP20's 23.28 m²/kg.
• Above setting 40, the two series move closer together and all reported values fall between 6.484 and 9.657 m²/kg.
• Higher surface area usually increases the area available to water, but it does not by itself guarantee a higher or better extraction. Flow, contact time and distribution still matter.

What the MP and F differences may taste like

Particle-size measurements do not taste the coffee, so they cannot prove a flavor note. They can, however, suggest a useful sensory direction to test. The combination of finer medians and higher measured surface area at the MP burr's fine end points toward an espresso-focused presentation; the F burr's filter-sized medians and generally lower relative Span point toward a clearer filter presentation.

Important: the burr does not create chocolate, fruit or floral notes; those come from the coffee and roast. Burr choice changes how easily those attributes may be expressed through a given recipe. A controlled blind cupping would be needed to verify these sensory expectations.

MP40 vs F40: same dial, different grind

A dial number is not a universal unit of grind size. Setting 40 is useful because both burrs were measured there under the same method.

Brew-method particle-size map

The brew-size reference used in this guide gives a suggested main particle-size band and center for each method. The map below includes a setting when its measured D50 falls inside that band. D50 is a useful comparison point, but it is not the same thing as a complete grind distribution or a brewing recipe.

*MP40 measures 448.4 μm D50, just 1.6 μm below the chart's V60 lower edge. “No tested D50 in band” means the closest measured point sits outside the reference band; it does not mean the grinder cannot brew that method.

Two practical starting regions

Why espresso and filter favor different burr directions

Espresso and pour-over ask the grinder to solve different flow problems. Espresso pushes water through a compact puck and produces a concentrated beverage in a short contact time. Filter brewing lets gravity move water through a more open bed over a longer period. That changes what “useful grind control” looks like.

The particle-size data lets us compare what comes out of each burr. It does not isolate every cause—geometry, alignment, RPM, seasoning and coffee can all affect the result—so the most useful conclusions are about measured range, recipe direction and starting position.

1. The MP dataset devotes more measured range to fine medians

Five MP samples—MP0 through MP20—have D50 values below 200 μm. Only F0 falls below that level. MP0 also reports the highest surface area in the complete set. This makes the MP option the more direct starting point for espresso-first users, consistent with the positioning on the current official product page.

2. The F dataset moves into filter-sized medians sooner

F30 reaches 421.1 μm D50, F40 reaches 495.0 μm and F60 reaches 577.5 μm. At the same settings, the MP values are 318.9, 448.4 and 515.3 μm. The F set therefore places more of its tested dial in the medium-fine and medium regions used for filter brewing.

3. The dial response is nonlinear

The size change is not constant across the dial. For example, MP20 to MP25 rises 48.3 μm, MP25 to MP30 rises 74.7 μm, and MP40 to MP50 rises only 28.8 μm. On the F burr, F60 to F70 rises 29.5 μm and F70 to F80 only 10.7 μm.

The practical lesson is simple: do not assume an equal particle-size change for every equal dial movement. Make smaller adjustments near a working recipe and judge the beverage response.

4. Overlap does not erase specialization

MP50–80 and F40–80 all land inside the V60 reference band by D50, while F10–20 also land inside the espresso reference band. This overlap demonstrates range, not interchangeability. The lower and upper percentiles, Span and surface area remain different, and a workable brew depends on more than the median.

Espresso vs filter: a deeper reading of the ranges

The brew-size reference used for this guide places espresso around a 200–400 μm main-particle band with an approximate 300 μm center, and V60 around 450–750 μm with an approximate 600 μm center. The closest tested GU64 settings give us a logical place to begin dialing in.

Particle-size-matched espresso region

Important boundary: this table answers “which samples match the D50 reference band?” It does not answer “which setting will pull a 25–30 second shot on every GU64?” Espresso flow depends on the complete distribution, burr calibration, beans, dose, basket, puck preparation, pressure and ratio. A user may need a much finer dial position than the chart-matched median suggests.

Particle-size-matched V60 region

F40 is a useful fine-side V60 option, while F60–70 sits closest to the ≈600 μm center. F80 has the lowest measured Span and is the coarsest practical starting point for larger filter brews.

For Chemex, French press and cold brew, start at F80 and adjust by flow and taste. Its measured D50 remains below the reference chart's center for those coarser methods, so treat 80 as the closest available starting point rather than a confirmed match.

Five evidence-led takeaways

1. The full distribution matters. Two samples with similar D50 can still have different D10, D90, Span and surface area. Median overlap is not the same as identical grind behavior.
2. Span is not a universal quality score. Lower Span describes a narrower relative percentile range, but the best result still depends on the brewing method and recipe.
3. The MP and F burrs have clear emphasis but real overlap. MP extends further into fine medians; F reaches medium medians sooner. Both can cover part of the filter range, and F can also reach espresso-sized medians at its fine end.
4. Settings are starting points, not transferable prescriptions. Coffee, roast, dose, RPM, calibration and equipment can all move the working position.
5. Taste is the final check. Use the table to choose a region, then adjust for flow, drawdown, strength and balance in the cup.

Which burr should you choose?

Choose MP for espresso-first routines

The MP burr gives more measured dial positions below 400 μm and is the current product page's espresso-led, multi-purpose option. It can also reach filter-sized D50 values at coarser settings, so it is the more direct choice if espresso is daily and pour-over is occasional.

Choose F for pour-over-first routines

The F burr reaches medium and medium-fine D50 values sooner across the measured dial and devotes settings 40–80 to the V60 reference band. Choose it when filter coffee is the center of your routine.

Do not confuse overlap with identical results

Both burrs can land at similar D50 values, but D50 describes only the median. D10, D90, distribution shape, alignment, RPM and the coffee itself still affect flow and extraction. A matching median does not promise a matching cup.

A better way to dial in

1. Choose the measured region closest to your brew method's reference band.
2. Keep coffee dose, water, temperature and technique stable.
3. Change the grinder in small increments.
4. Use beverage flow and taste as the final decision, not the table alone.
5. Record the useful position for each coffee and recipe.

Watch the official GU64 instructional videos →

Frequently asked questions

Precision meets flavor

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